To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
In a multi-user massive MIMO system serving a plurality of users at the same time, accurate channel state information at a transmitter (CSIT) needs to be obtained in order to secure spectral efficiency in massive MIMO. To this end, however, radio resources are required for a large number of reference signals and a large quantity of channel state information feedback (e.g., a precoding matrix indicator (PMI), a rank indicator (RI), and channel quality information (CQI)). Further, as the number of users capable of being simultaneously served with a massive transmission antenna is significantly increasing, there is a practical problem of remarkably increased complexity in precoding calculation compared to the prior art. Therefore, it is required to design a beamformer for effectively controlling interference and for reinforcing transmission power. Further, a beamformer for a multi-cell massive MIMO system is effective in interference control when jointly designed in association with cooperative communication and coordinated multi-points (CoMP), and thus a joint design in association with cooperative communication/CoMP is required for a beamformer.